U.S. patent application number 16/282878 was filed with the patent office on 2019-08-29 for position measurement apparatus, position correction method, and position information acquisition system.
The applicant listed for this patent is SHARP KABUSHIKI KAISHA. Invention is credited to HAJIME KUBOTA, YOSHIHISA SEKIGUCHI.
Application Number | 20190265037 16/282878 |
Document ID | / |
Family ID | 67685723 |
Filed Date | 2019-08-29 |
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United States Patent
Application |
20190265037 |
Kind Code |
A1 |
KUBOTA; HAJIME ; et
al. |
August 29, 2019 |
POSITION MEASUREMENT APPARATUS, POSITION CORRECTION METHOD, AND
POSITION INFORMATION ACQUISITION SYSTEM
Abstract
In a position measurement apparatus, to maintain accuracy of a
trajectory even when the frequency of acquisition of absolute
position information is reduced, a movement information generation
unit generates movement information including a movement distance
and a movement direction of a device of interest based on a sensor
value, and a reliability generation unit generates reliability
information indicating a reliability value of the movement
information. An amount of distance correction and an amount of
angle correction to be made every predetermined number of steps are
determined based on the reliability information and the movement
information, and the distance and the angle are corrected every
predetermined number of steps starting from the latest
already-corrected position information.
Inventors: |
KUBOTA; HAJIME; (Sakai City,
JP) ; SEKIGUCHI; YOSHIHISA; (Sakai City, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
SHARP KABUSHIKI KAISHA |
Sakai City |
|
JP |
|
|
Family ID: |
67685723 |
Appl. No.: |
16/282878 |
Filed: |
February 22, 2019 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
G01S 5/0263 20130101;
G01S 5/0294 20130101; G01S 5/02 20130101; G01S 19/49 20130101; G01C
21/14 20130101; G01C 22/00 20130101; G01C 21/165 20130101; G01S
19/393 20190801; H04W 4/026 20130101; G01C 21/005 20130101 |
International
Class: |
G01C 21/00 20060101
G01C021/00; G01C 21/14 20060101 G01C021/14; G01S 19/49 20060101
G01S019/49; G01C 22/00 20060101 G01C022/00; H04W 4/02 20060101
H04W004/02 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 27, 2018 |
JP |
2018-033658 |
Jan 25, 2019 |
JP |
2019-011270 |
Claims
1. A position measurement apparatus comprising: a position
estimation unit configured to estimate a position of a device of
interest based on a sensor value acquired from a sensor; an
absolute coordinate measurement unit configured to measure absolute
coordinates of the device of interest; and a correction processing
unit configured to correct the position of the device of interest
estimated by the position estimation unit based on the absolute
coordinates of the device of interest measured by the absolute
coordinate measurement unit, the position estimation unit including
an attitude information generation unit configured to generate
attitude information associated with the device of interest based
on the sensor value, a movement information generation unit
configured to generate, based on the attitude information, movement
information including a movement distance of the device of interest
and a movement direction of the device of interest, and a
reliability generation unit configured to generate, based on the
sensor value, reliability information indicating a reliability
value of the movement information, the correction processing unit
being configured to determine an amount of distance correction to
be made every predetermined number of steps and an amount of angle
correction to be made every predetermined number of steps based on
the reliability information and the movement information, and
correct the movement distance and the movement direction every
predetermine number of steps starting from latest already-corrected
position information associated with the device of interest.
2. The position measurement apparatus according to claim 1, wherein
the movement information generation unit generates information
associated with the movement direction by performing a principal
component analysis on a horizontal acceleration included in the
attitude information, and the reliability generation unit generates
a reliability value of an angle from a ratio of a first principal
component to a second principal component included in the
information associated with the movement direction.
3. The position measurement apparatus according to claim 1, wherein
the sensor includes a gyro sensor and a geomagnetic sensor, the
movement information generation unit generates the information
associated with the movement direction by integrating a value
acquired from the gyro sensor, and the reliability generation unit
generates a reliability value of an angle by calculating a
difference between the information associated with the movement
direction obtained by integrating the value obtained from the gyro
sensor and information associated with the movement direction
acquired from the geomagnetic sensor.
4. The position measurement apparatus according to claim 1, wherein
the sensor includes a geomagnetism sensor, the movement information
generation unit generates the information associated with the
movement direction from a resultant vector of vectors along three
axes obtained from the geomagnetic sensor, and the reliability
generation unit generates a reliability value of an angle by
calculating an amount of change of the information associated with
the movement direction obtained from a magnitude of the resultant
vector of vectors along three axes obtained from the geomagnetic
sensor.
5. The position measurement apparatus according to claim 1, wherein
the sensor includes a geomagnetism sensor, the movement information
generation unit generates the information associated with the
movement direction from a magnetic inclination of the geomagnetic
sensor, and the reliability generation unit generates a reliability
value of an angle by calculating an amount of change of the
information associated with the movement direction obtained from
the magnetic inclination of the geomagnetic sensor.
6. The position measurement apparatus according to claim 1, wherein
the sensor includes a gyro sensor, the movement information
generation unit generates the information associated with the
movement direction by differentiating a value acquired from the
gyro sensor, and the reliability generation unit generates a
reliability value of an angle by calculating an amount of change of
the information associated with the movement direction obtained
from derivatives along the three axes of the gyro sensor.
7. The position measurement apparatus according to claim 1, wherein
the sensor includes an acceleration sensor and a geomagnetic
sensor, the attitude information generation unit generates attitude
information corresponding to a sensor value of the acceleration
sensor and a sensor value of the geomagnetic sensor, and the
reliability generation unit generates a reliability value of an
angle from a difference in angle between the attitude information
corresponding to the sensor value of the acceleration sensor and
the attitude information corresponding to the sensor value of the
geomagnetic sensor.
8. The position measurement apparatus according to claim 1, wherein
the sensor includes an acceleration sensor, a geomagnetic sensor,
and a gyro sensor, the attitude information generation unit
generates attitude information by using a combination of the
acceleration sensor and the geomagnetic sensor, and the gyro
sensor, and the reliability generation unit generates a reliability
value of an angle from a difference in azimuth angle between the
attitude information obtained by the gyro sensor and the attitude
information obtained by the combination of the acceleration sensor
and the geomagnetic sensor.
9. The position measurement apparatus according to claim 1, wherein
the sensor includes an acceleration sensor and an atmospheric
pressure sensor, the movement information generation unit generates
information associated with the movement distance from an amount of
change of a sensor value obtained from the atmospheric pressure
sensor and generates information associated with the movement
distance from an amount of change in a vertical direction of a
sensor value obtained from the acceleration sensor, and the
reliability generation unit generates a reliability value of the
distance from a difference between the distance obtained by the
atmospheric pressure sensor and the distance obtained by the
acceleration sensor.
10. The position measurement apparatus according to claim 1,
wherein the sensor includes an acceleration sensor, the movement
information generation unit generates the information associated
with the movement distance from an amount of change of a velocity
obtained by dividing a value of the acceleration sensor by a moving
time taken for the user to move a predetermined number of steps,
and the reliability generation unit generates the reliability value
of the distance from a difference, from an average moving time of
the user, of information associated with the movement distance
obtained from an amount of change of a velocity obtained by
dividing a value of the acceleration sensor by a moving time taken
for the user to move a predetermined number of walking steps.
11. The position measurement apparatus according to claim 1,
wherein the sensor includes at least one of a gyro sensor, a
geomagnetic sensor, and acceleration sensor, and an atmospheric
pressure sensor, the reliability generation unit performs a
combination of plurality of processes selected from a group
including a process of generating a reliability value of an angle
from a ratio of a first principal component of information
associated with the movement direction to a second principal
component of the information associated with the movement
direction, a process of generating a reliability value of an angle
by calculating a difference between information associated with the
movement direction obtained by integrating a value acquired from
the gyro sensor and information associated with the movement
direction acquired from the geomagnetic sensor, a process of
generating a reliability value of an angle by calculating an amount
of change of information associated with the movement direction
obtained from a magnitude of a resultant vector of vectors along
three axes of the geomagnetic sensor, a process of generating a
reliability value of an angle by calculating an amount of change of
information associated with the movement direction obtained from a
magnetic inclination of the geomagnetic sensor, a process of
generating a reliability value of an angle by calculating an amount
of change of information associated with the movement direction
obtained from derivatives along three axes of the gyro sensor, a
process of generating a reliability value of an angle from a
difference in angle between attitude information corresponding to a
sensor value of the acceleration sensor and attitude information
corresponding to a sensor value of the geomagnetic sensor, a
process of generating a reliability value of a distance from a
difference between a movement distance obtained from an amount of
change of the atmospheric pressure sensor and a movement distance
obtained from an amount of change of the acceleration sensor, and a
process of generating a reliability value of a distance from a
difference between an average moving time of a user and information
associated with the movement distance obtained from an amount of
change of a velocity obtained by dividing a value of the
acceleration sensor by a moving time taken for the user to move a
predetermined number of steps.
12. The position measurement apparatus according to claim 1,
wherein the absolute coordinate measurement unit measures the
absolute coordinates by acquiring a GPS signal.
13. The position measurement apparatus according to claim 1,
wherein the absolute coordinate measurement unit measures the
absolute coordinates by receiving a beacon radio wave.
14. The position measurement apparatus according to claim 1,
wherein the absolute coordinate measurement unit measures the
absolute coordinates by receiving a Wi-Fi radio wave.
15. The position measurement apparatus according to claim 1,
wherein the absolute coordinate measurement unit measures the
absolute coordinates by acquiring an image marker.
16. A position correction method comprising: estimating a position
of a device of interest based on a sensor value acquired by a
sensor; measuring absolute coordinates of the device of interest;
and correcting the estimated position of the device of interest
based on the absolute coordinates of the device of interest, the
estimating of the position including generating attitude
information associated with the device of interest based on the
sensor value, generating movement information including a movement
distance of the device of interest and a movement direction of the
device of interest based on the attitude information, and
generating reliability information indicating a reliability value
of the movement information based on the sensor value, the
correcting including determining an amount of distance correction
to be made every predetermined number of steps and an amount of
angle correction to be made every predetermined number of steps
based on the reliability information and the movement information,
and correcting the movement distance and the movement direction
every predetermine number of steps starting from latest
already-corrected position information associated with the device
of interest.
17. A position information acquisition system comprising: the
position measurement apparatus according to claim 1; and an
installed terminal having installation coordinate information, the
position measurement apparatus being configured to acquire the
absolute coordinates by acquiring the installation coordinate
information from the installed terminal.
Description
BACKGROUND
1. Field
[0001] The present disclosure relates to a position measurement
apparatus, a position correction method, and a position information
acquisition system.
2. Description of the Related Art
[0002] In portable terminal apparatuses such as a portable
telephone or the like, a technique of measuring a position using a
GPS (Global Positioning System) function is generally used.
However, the position measurement using the GPS function consumes
large electric power, which may result in a reduction in battery
life.
[0003] In view of the above, a technique to reduce consumption
power to a relatively low level has been proposed. In this proposed
technique, a walking path or a moving path of the user is estimated
using an autonomous navigation technique while a GPS function is
intermittently executed thereby achieving a reduction in
consumption power (see, for example, International Publication No.
WO2014/156385 (laid open Feb. 10, 2014), Japanese Unexamined Patent
Application Publication No. 2012-233731 (laid open Nov. 29,
2012)).
[0004] In order to increase estimation accuracy of a moving path
while minimizing the use of the GPS function to suppress
consumption power, it has been proposed to use a walking trajectory
interpolation technique using a spring model (see, for example,
Japanese Unexamined Patent Application Publication No. 2012-122892
(laid open Jun. 28, 2012)).
[0005] A rotation and/or enlargement/reduction are generally
performed to correct a moving path estimated by the autonomous
navigation using absolute position information acquired by the GPS
function. However, operating the GPS function intermittently to
reduce the consumption power may make it difficult to achieve
high-enough accuracy in correction according to a known related
technique.
[0006] The present disclosure provides a technique of achieving a
high trajectory accuracy even when the frequency of acquisition of
absolute position information is reduced.
SUMMARY
[0007] In an aspect of the present disclosure, a position
measurement apparatus includes a position estimation unit
configured to estimate a position of a device of interest based on
a sensor value acquired from a sensor, an absolute coordinate
measurement unit configured to measure absolute coordinates of the
device of interest, and a correction processing unit configured to
correct the position of the device of interest estimated by the
position estimation unit based on the absolute coordinates of the
device of interest measured by the absolute coordinate measurement
unit, the position estimation unit including an attitude
information generation unit configured to generate attitude
information associated with the device of interest based on the
sensor value, a movement information generation unit configured to
generate, based on the attitude information, movement information
including a movement distance of the device of interest and a
movement direction of the device of interest, and a reliability
generation unit configured to generate, based on the sensor value,
reliability information indicating a reliability value of the
movement information, the correction processing unit being
configured to determine a distance correction amount every
predetermined number of steps and an angle correction amount every
predetermined number of steps based on the reliability information
and the movement information, and correct the movement distance and
the movement direction every predetermine number of steps starting
from latest already-corrected position information associated with
the device of interest.
[0008] In an aspect of the present disclosure, a position
correction method includes estimating a position of a device of
interest based on a sensor value acquired by a sensor, measuring
absolute coordinates of the device of interest; and, correcting the
estimated position of the device of interest based on the absolute
coordinates of the device of interest, the estimating of the
position including generating attitude information associated with
the device of interest based on the sensor value, generating
movement information including a movement distance of the device of
interest and a movement direction of the device of interest based
on the attitude information, and generating reliability information
indicating a reliability value of the movement information based on
the sensor value, the correction processing unit being configured
to determine, based on the reliability information and the movement
information, an amount of distance correction to be made every
predetermined number of steps and an amount of angle correction to
be made every predetermined number of steps, and correcting the
movement distance and the movement direction every predetermine
number of steps starting from latest already-corrected position
information associated with the device of interest.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] FIG. 1 is a block diagram schematically illustrating an
example of a configuration of a position measurement apparatus
according to a first embodiment of the present disclosure;
[0010] FIG. 2 is a diagram illustrating an example of a manner in
which a position measurement apparatus is worn according to a first
embodiment of the present disclosure;
[0011] FIG. 3 is a diagram illustrating an inclination angle and an
azimuth angle used in calculating an attitude according to the
first embodiment of the present disclosure;
[0012] FIG. 4 is a diagram illustrating a movement vector used by a
relative coordinate calculation unit according to the first
embodiment of the present disclosure;
[0013] FIG. 5 is a diagram illustrating the magnitude of each
component of principal component analysis used by a reliability
generation unit in calculating angle reliability value according to
the first embodiment of the present disclosure;
[0014] FIG. 6 is a diagram illustrating variables used by a
trajectory correction unit according to the first embodiment of the
present disclosure;
[0015] FIG. 7 is a diagram illustrating a moving path including a
gyro sensor abnormality, for use in explaining usefulness of the
first embodiment of the present disclosure;
[0016] FIG. 8 is a diagram illustrating a manner in which a moving
path illustrated in FIG. 7 is corrected according to a known
trajectory correction process;
[0017] FIG. 9 is a diagram illustrating a manner in which a moving
path illustrated in FIG. 7 is corrected using a trajectory
correction process according to the first embodiment of the present
disclosure;
[0018] FIG. 10 is a diagram illustrating a moving path including a
magnetic anomaly, for use in explaining usefulness of the first
embodiment of the present disclosure;
[0019] FIG. 11 is a diagram illustrating a manner in which a moving
path illustrated in FIG. 10 is corrected according to a known
trajectory correction process;
[0020] FIG. 12 is a diagram illustrating a manner in which a moving
path illustrated in FIG. 10 is corrected using a trajectory
correction process according to the first embodiment of the present
disclosure;
[0021] FIG. 13 is a flow chart illustrating a flow of a process of
calculating a reliability value of a position measurement
apparatus;
[0022] FIG. 14 is a diagram illustrating a manner of calculating a
reliability value of an angle;
[0023] FIGS. 15A and 15B are diagrams each illustrating reliability
of an angle;
[0024] FIG. 16 is a flow chart illustrating a flow of a process of
calculating a correction amount of a position measurement
apparatus;
[0025] FIG. 17 is a block diagram schematically illustrating an
example of a configuration of a position measurement apparatus
according to a second embodiment of the present disclosure;
[0026] FIG. 18 is a block diagram schematically illustrating an
example of a configuration of a position measurement apparatus
according to a third embodiment of the present disclosure;
[0027] FIG. 19 is a block diagram schematically illustrating an
example of a configuration of a position measurement apparatus
according to a fourth embodiment of the present disclosure;
[0028] FIGS. 20A, 20B, and 20C are diagrams illustrating an example
of a behavior of a gyro sensor in walking according to a sixth
embodiment of the present disclosure;
[0029] FIG. 21 is a diagram illustrating an example of a position
information acquisition system according to an embodiment of the
present disclosure; and
[0030] FIG. 22 is a diagram illustrating an example of a position
information acquisition system according to an embodiment of the
present disclosure.
DESCRIPTION OF THE EMBODIMENTS
First Embodiment
[0031] A position measurement apparatus 1 according to a first
embodiment of the present disclosure is described in detail below.
The position measurement apparatus 1 is an apparatus configured to
measure a position of a device of interest capable of being carried
by a user such as a portable navigation apparatus, a smartphone, or
the like, thereby maintaining high accuracy of a trajectory of a
moving path dependent on a movement of the user.
[0032] Note that in the following description, it is assumed by way
of example that the position measurement apparatus 1 is installed
integrally with the device of interest whose position is to be
measured, that is, the device of interest itself is the position
measurement apparatus 1. However, the manner of installing the
position measurement apparatus 1 is not limited to this example,
but the position measurement apparatus 1 may be installed, for
example, on a server that receives a sensor value from a sensor
disposed on the device of interest and the position measurement
apparatus 1 may transmit information associated with the measured
position of the device of interest to the device of interest.
[0033] FIG. 2 is a diagram illustrating an example of a manner in
which the position measurement apparatus 1 is worn. In the
configuration in which the position measurement apparatus 1 is
installed integrally with the device of interest whose position is
to be measured, the position measurement apparatus 1 may be worn on
a waist or the like of the user such that the position measurement
apparatus 1 is located higher than the user's groin as shown in
FIG. 2. The position measurement apparatus 1 acquires information
associated with the attitude of the position measurement apparatus
1 depending on the movement of the user and measure the position of
the position measurement apparatus 1.
Outline of Configuration of Position Measurement Apparatus 1
[0034] FIG. 1 is a block diagram schematically illustrating an
example of a configuration of the position measurement apparatus 1
according to the first embodiment.
[0035] The position measurement apparatus 1 includes a position
estimation unit 11, an absolute coordinate measurement unit 12, and
a correction processing unit 13.
Configuration of Position Estimation Unit 11
[0036] The position estimation unit 11 includes a sensor group 111
including a plurality of sensors, and has a function of estimating
the position of the position measurement apparatus 1 by using, for
example, an autonomous navigation technique. The position
estimation unit 11 estimates the position of the position
measurement apparatus 1 based on sensor values acquired by the
respective sensors in the sensor group 111.
[0037] The sensor group 111 includes an acceleration sensor 1111, a
geomagnetic sensor 1112, a gyro sensor 1113, and an atmospheric
pressure sensor 1114.
[0038] The acceleration sensor 1111 is influenced by an
acceleration of gravity. That is, even in a non-operating state,
the vertical components of the sensor values of the acceleration
sensor 1111 are influenced by the acceleration of gravity. Using
this fact, the position estimation unit 11 is capable of
determining the wearing attitude of the position measurement
apparatus 1 based on sensor values acquired by the acceleration
sensor 1111.
[0039] The sensor values acquired by the acceleration sensor 1111
vary depending on a movement of the user. By integrating the sensor
values acquired by the acceleration sensor 1111, it is possible to
obtain information associated with the velocity of the moving of
the position measurement apparatus 1. By further integrating the
integrated values of the sensor values acquired by the acceleration
sensor 1111, it is possible to obtain information associated with
the movement distance of the position measurement apparatus 1.
[0040] The geomagnetic sensor 1112 is a sensor configured to
measure a magnetic flux density. The position estimation unit 11 is
capable of determining a magnetic north direction based on the
sensor values acquired by the geomagnetic sensor 1112. Note that it
is known that when an object that generates a magnetic field exists
near the geomagnetic sensor 1112, the geomagnetic sensor 1112 is
influenced by this magnetic field.
[0041] The gyro sensor 1113 is a sensor configured to measure an
angular velocity that occurs in a rotational movement. The position
estimation unit 11 is capable of obtaining a rotation angle by
integrating the sensor value of the gyro sensor 1113 that occurs in
a rotational movement. Furthermore, by setting an initial direction
(an initial angle) in the gyro sensor 1113 in a state in which
there is no rotational movement, it becomes possible to detect the
magnetic north direction, and to acquire a rotation angle with
respect to the magnetic north direction based on the sensor values
acquired from the gyro sensor 1113.
[0042] The atmospheric pressure sensor 1114 is a sensor configured
to measure an atmospheric pressure in an ambient environment. Based
on the sensor value acquired by the atmospheric pressure sensor
1114, the position estimation unit 11 is capable of calculating a
movement distance of the position measurement apparatus 1 in the
vertical direction, using the fact that the atmospheric pressure
varies depending on a change in the height. Note that it is known
that a change in a sensor value of the atmospheric pressure sensor
1114 can occur when a change occurs in an environment such as
weather or when the atmospheric pressure sensor 1114 enters or
exits a closed space.
[0043] The position estimation unit 11 further includes an attitude
information generation unit 112 configured to generate attitude
information associated with the position measurement apparatus 1
based on the sensor values detected by the respective sensors 1111,
1112, 1113, and 1114 of the sensor group 111. The position
estimation unit 11 also includes a movement information generation
unit 118 configured to generate movement information including a
movement distance and a movement direction of the position
measurement apparatus 1 based on the attitude information generated
by the attitude information generation unit 112. The position
estimation unit 11 also includes a reliability generation unit 115
configured to generate reliability information indicating a
reliability value of the movement information generated by the
movement information generation unit 118 based on the sensor values
detected by the respective sensors 1111, 1112, 1113, and 1114 of
the sensor group 111 and the attitude information generated by the
attitude information generation unit 112. The position estimation
unit 11 also includes a relative coordinate calculation unit 116
configured to calculate a relative position of the position
measurement apparatus 1 in latitude and longitude based on the
movement information generated by the movement information
generation unit 118.
[0044] The attitude information generation unit 112 generates
attitude information associated with the position measurement
apparatus 1 based on at least one of the sensor values detected by
the acceleration sensor 1111, the geomagnetic sensor 1112, and the
gyro sensor 1113.
[0045] FIG. 3 is a diagram illustrating a relationship between the
attitude of the position measurement apparatus 1 and the
inclination angle and azimuth angle representing the attitude. For
example, as illustrated in FIG. 3, the attitude information
generation unit 112 calculates the inclination angle of the
attitude of the position measurement apparatus 1 with respect to a
direction from the zenith based on the sensor value of the
acceleration sensor 1111. Furthermore, the position measurement
apparatus 1 calculates the azimuth angle, which is an angle about
an axis defined in the zenith direction based on the sensor value
of the gyro sensor 1113 in which the initial angle is set, and the
sensor value of the geomagnetic sensor 1112.
[0046] The attitude information generation unit 112 is capable of
generating attitude information indicating the attitude of the
position measurement apparatus 1 indicated by the inclination angle
with respect to the zenith direction and the azimuth angle based on
the sensor values of the acceleration sensor 1111 the geomagnetic
sensor 1112, and the gyro sensor 1113, even when the position
measurement apparatus 1 is in any attitude.
[0047] The gyro sensor 1113 and the geomagnetic sensor 1112 each
have a sensor-specific offset value. Furthermore, there is a
possibility that the geomagnetic sensor 1112 is influenced by a
magnetic field as described above. The attitude information
generation unit 112 calculates the attitude of the position
measurement apparatus 1 from the sensor value acquired by the
acceleration sensor 1111 and the sensor value acquired by the
geomagnetic sensor 1112. The attitude information generation unit
112 also calculates the attitude of the position measurement
apparatus 1 using the sensor value of the gyro sensor 1113. The
attitude information generation unit 112 selects one attitude from
the two calculated attitudes by using a Kalman filter or the like
thereby obtaining a single most likelihood angle.
[0048] The attitude information generation unit 112 performs an
affine transformation on the inclination angle from the zenith
direction and the azimuth angle of the position measurement
apparatus 1 thereby performing a coordinate axis transformation on
the calculated attitude from the sensor axis coordinate system to
the absolute coordinate system and generating attitude information.
The attitude information generation unit 112 provides the generated
attitude information to the movement information generation unit
118 and the reliability generation unit 115.
[0049] The movement information generation unit 118 includes a
movement direction calculation unit 113 configured to calculate the
movement direction of the position measurement apparatus 1, and a
movement distance calculation unit 114 configured to calculate the
movement distance of the position measurement apparatus 1.
[0050] The movement direction calculation unit 113 performs a
principal component analysis on the horizontal acceleration
included in the attitude information generated by the attitude
information generation unit 112, thereby generating information
indicating the movement direction given by the first principal
component. In general, when an object moves, the acceleration
changes only in its movement direction. However, when a human being
walks, he/she moves left and right feet alternately and thus
his/her body sways to the left and right. As a result, the
acceleration also changes in a direction different from the
traveling direction. However, the change in the acceleration in the
traveling direction is greater than in a direction difference from
the traveling direction. Therefore, by performing the principal
component analysis on the horizontal acceleration, it is possible
to determining the actual (principal) movement direction. The
movement direction calculation unit 113 provides the information
associated with the movement direction to the relative coordinate
calculation unit 116.
[0051] On the other hand, in the case of an unusual walking manner,
for example, in which the body sways largely to the left and right,
the error in the determination of the movement direction tends to
become large, which may cause a reduction in accuracy of the
movement trajectory. To handle the above situation, in the present
embodiment, the information associated with the movement direction
calculated by the movement direction calculation unit 113 is
provided to the reliability generation unit 115, which generates
the reliability information indicating the reliability value of the
information associated with the movement direction.
[0052] The movement distance calculation unit 114 calculates the
length of stride of the user by using the change in the
acceleration in the vertical direction included in the attitude
information generated by the attitude information generation unit
112 thereby acquiring the movement distance of the user every
walking step. Note that alternatively the movement distance
calculation unit 114 may calculate the movement distance from the
acceleration information by any known technique. The movement
distance calculation unit 114 provides the information associated
with the calculated movement distance to the relative coordinate
calculation unit 116 and the reliability generation unit 115.
[0053] The relative coordinate calculation unit 116 calculates the
relative position of the position measurement apparatus 1 based on
a movement vector represented by the movement information including
the movement direction and the movement distance respectively
calculated by the movement direction calculation unit 113 and the
movement distance calculation unit 114. FIG. 4 is a diagram
illustrating a movement vector used by the relative coordinate
calculation unit 116. As illustrated in FIG. 4, the relative
coordinate calculation unit 116 decomposes the movement vector into
vectors respectively pointing north and east, and determines the
latitude and longitude according to a known formula (see, for
example, at a web site of Geographical Survey Institute
(http://www.gsi.go.jp/index.html)). The relative coordinate
calculation unit 116 provides the calculated relative position of
the position measurement apparatus 1 to the correction processing
unit 13.
Reliability Generation Unit 115
[0054] The reliability generation unit 115 generates reliability
information indicating the reliability value of the attitude
information and the reliability value of the movement information
based on the attitude information generated by the attitude
information generation unit 112 and the movement information
generated by the movement information generation unit 118. The
reliability value is calculated, for example, from an error caused
by an environment in which the sensor values of the respective
sensors 1111, 1112, 1113, and 1114 of the sensor group 111, or an
error that occurs when the attitude information and the movement
information are calculated based on the sensor values described
above.
[0055] The reliability generation unit 115 estimates the angle
reliability value indicating a degree of an error of the angle
which occurs in the calculated direction in which the user moves in
every walking step, and estimates the distance reliability value
indicating a degree of an error of the distance which occurs in the
calculated distance of the movement of the user in each walking
step. The reliability generation unit 115 estimates the reliability
values in terms of the angle made by the user in every walking step
and the distance moved by the user in every walking step. Note that
the reliability values are used later in a trajectory correction.
This makes it possible to correct a local trajectory. Note that the
distance moved by the user every walking step is equal to the
length of stride of the user. In the following description, the
length of stride corresponds to the distance moved by the user
every walking step.
[0056] Furthermore, in the following description, it is assumed by
way of example that the reliability generation unit 115 estimates
the angle reliability value every walking step of the user and the
distance reliability value every walking step of the user. However,
instead of estimating the reliability value every walking step, the
reliability generation unit 115 may estimate the angle reliability
value every predetermined number of steps and the distance
reliability value every predetermined number of steps.
[0057] The reliability generation unit 115 includes an angle
reliability generation unit 1151 and a distance reliability
generation unit 1152.
[0058] The angle reliability generation unit 1151 generates an
angle reliability value based on the attitude information generated
by the attitude information generation unit 112 and the information
associated with the movement direction every walking step of the
user calculated by the movement direction calculation unit 113.
[0059] The angle reliability generation unit 1151 generates the
angle reliability value of the attitude information by determining
the difference in azimuth angle between attitude information
generated based on a combination of the sensor value of the
acceleration sensor 1111 and the sensor value of the geomagnetic
sensor 1112 from the attitude information generated based on the
sensor value of the gyro sensor 1113. For example, the angle
reliability generation unit 1151 may determine the angle
reliability value of the attitude information as 1/|degG-degM|
where degG is the azimuth angle calculated based on the sensor
value of the gyro sensor 1113 and degM is the azimuth angle
calculated based on the sensor value of the geomagnetic sensor
1112.
[0060] FIG. 5 is a diagram illustrating the magnitude of each
component of the horizontal acceleration for use in generating the
angle reliability value. The angle reliability generation unit 1151
generates the angle reliability value in the movement direction
every walking step of the user by using the ratio of the second
principal component to the first principal component of the
horizontal acceleration calculated by the movement direction
calculation unit 113. For example, the angle reliability generation
unit 1151 may determine the angle reliability value in the movement
direction every walking step of the user as S1/S2 where S1 is the
magnitude of the first principal component of the horizontal
acceleration and S2 is the magnitude of the second principal
component as illustrated in FIG. 5.
[0061] The angle reliability generation unit 1151 generates the
angle reliability value of the position information associated with
the user based on the angle reliability value of the attitude
information and the angle reliability value in the movement
direction every walking step of the user. The angle reliability
generation unit 1151 determines the angle reliability value .alpha.
in the position information associated with the user as
.alpha.=(.alpha..sub.A*.alpha..sub.B)/(.alpha..sub.A+.alpha..sub.-
B) where .alpha..sub.A is the angle reliability value of the
attitude information and .alpha..sub.B is the angle reliability
value in the movement direction every walking step of the user.
[0062] The distance reliability generation unit 1152 generates the
distance reliability value based on the information associated with
the movement distance moved by the user every walking step
calculated by the movement distance calculation unit 114.
[0063] The distance reliability generation unit 1152 generates the
distance reliability value of the movement distance made by the
user every walking step by calculating the difference between the
vertical movement distance calculated based on the sensor value of
the atmospheric pressure sensor 1114 and the movement distance in
the vertical direction calculated based on the sensor value of the
acceleration sensor 1111.
[0064] For example, the distance reliability generation unit 1152
determines the distance La in the vertical direction that occurs
each time the user walks one step from the vertical acceleration
calculated by the movement distance calculation unit 114.
Furthermore, the distance reliability generation unit 1152
determines the amount of change Lp in the distance from the amount
of change in atmospheric pressure acquired based on the sensor
value of the atmospheric pressure sensor 1114. The distance
reliability generation unit 1152 then determines the distance
reliability value as 1/|La-Lp|.
[0065] The angle reliability generation unit 1151 and the distance
reliability generation unit 1152 respectively provides the angle
reliability value and the distance reliability value, which are
reliability information indicating the reliability value of the
movement information, to the correction processing unit 13.
[0066] In the present embodiment, two kinds of reliability values,
that is, the angle reliability value generated by the angle
reliability generation unit 1151 and the distance reliability value
generated by the distance reliability generation unit 1152 are used
by way of example but not limitation. For example, only one of the
angle reliability value and the distance reliability value may be
used. In this case, an unused reliability value may be fixed to 1,
and only the other reliability value may be used.
[0067] In a case where the value of the distance reliability value
is fixed to 1, a local distance correction every walking step of
the user may not be performed, but a global correction may be
performed uniformly on the whole trajectory, and a local correction
on the angle may be performed every one step of the user.
Configuration of Absolute Coordinate Measurement Unit 12
[0068] The absolute coordinate measurement unit 12 includes a GPS
sensor 121 configured to receive a GPS signal, and determines a
current position of the position measurement apparatus 1 from the
signal received via the GPS sensor 121. Thus, by acquiring the GPS
signal via the GPS sensor 121, the absolute coordinate measurement
unit 12 measures absolute coordinates that indicate the current
position of the position measurement apparatus 1 in latitude and
longitude. The absolute coordinate measurement unit 12 provides the
measured absolute coordinates of the position measurement apparatus
1 to the correction processing unit 13.
[0069] The configuration of the absolute coordinate measurement
unit 12 is not limited to the example described above in which the
absolute coordinates are measured from the received GPS signal.
FIGS. 17 to 19 each illustrate an example of another configuration
of the absolute coordinate measurement unit 12.
[0070] In the example illustrated in FIG. 17, the absolute
coordinate measurement unit 12 includes a beacon receiver 122
configured to receive a radio wave or an infrared ray transmitted
from a beacon installed on a road, thereby measuring absolute
coordinates. The absolute coordinate measurement unit 12 may
acquire absolute coordinates such that when a radio wave or a
infrared ray transmitted from a beacon is received by the beacon
receiver 122, if the strength thereof is greater than a
predetermined threshold value, the absolute coordinate measurement
unit 12 acquires installation coordinates of the beacon as the
absolute coordinates.
[0071] In the example illustrated in FIG. 18, the absolute
coordinate measurement unit 12 includes a Wi-Fi receiver 123
configured to receive a Wi-Fi radio wave thereby measuring absolute
coordinates. The absolute coordinate measurement unit 12 may
receive a plurality of Wi-Fi (registered trademark) radio waves via
the Wi-Fi receiver 123, and may calculate coordinates of the
current position from coordinate information and radio wave
strength information from each base station using a triangulation
technique thereby determining absolute coordinates.
[0072] The absolute coordinate measurement unit 12 may measure
absolute coordinates by acquiring an image marker. In the example
illustrated in FIG. 19, the absolute coordinate measurement unit 12
includes a camera 124, and acquires an image marker by analyzing an
image captured by the camera 124 thereby acquiring installation
coordinates of the image marker. The acquired installation
coordinates of the image marker are employed as the absolute
coordinates. The camera 124 may be installed on the position
measurement apparatus 1 such that the camera 124 is capable of
automatically capturing an image of surroundings when the position
measurement apparatus 1 is moving. When the absolute coordinate
measurement unit 12 finds a pattern of an installed image marker in
an image captured by the camera 124 and when the size of the
recognized image marker in the image is greater than a particular
value, the absolute coordinate measurement unit 12 may determine
that the absolute coordinate measurement unit 12 is located close
to the position of the image marker, and may employ installation
coordinates of the image marker as the absolute coordinates.
[0073] The absolute coordinate measurement unit 12 may measure
absolute coordinates using one of or a combination of the
following: the GPS sensor 121; the beacon receiver 122; the Wi-Fi
receiver 123; and the camera 124.
[0074] The position measurement apparatus 1 may function as a
position information acquisition system used together with an
installed terminal 2 having installation coordinate information
such as a beacon, Wi-Fi (registered trademark), an image marker or
the like, and may acquire absolute coordinates of the position
measurement apparatus 1 by acquiring, from the installed terminal
2, information associated with the installation coordinates of the
installed terminal 2.
[0075] FIG. 21 illustrates a position information acquisition
system in which the installed terminal 2 is a beacon, an image
marker, or the like. For example, the installed terminal 2 is
installed in a store. When the user wearing the position
measurement apparatus 1 comes near this store, the position
measurement apparatus 1 receives absolute coordinates of the
installed terminal 2 installed in the store and thus the position
measurement apparatus 1 detects that the user is located close to
the store.
[0076] In the example illustrated in FIG. 21, it is assumed by way
of example that the user wearing the position measurement apparatus
1 walks in a coverage area of a radio wave or an infrared ray
transmitted by the installed terminal 2 installed in a store A. In
FIG. 21, a broken circular line indicates the coverage area of the
radio wave or the infrared ray transmitted by the installed
terminal 2. When the user walks in the coverage area of the radio
wave or the infrared ray transmitted by the installed terminal 2
installed in the store A, the position measurement apparatus 1
receives absolute coordinates transmitted from the installed
terminal 2 installed in the store A. The position measurement
apparatus 1 may also receive, for example, an advertisement or the
like of the store A together with the absolute coordinates.
[0077] In response to receiving the absolute coordinates, the
position measurement apparatus 1 may output information associated
with a trajectory of a moving path of the user to the installed
terminal 2. The information associated with the trajectory may
indicate, for example, a path along which the user reaches the
store. In the example illustrated in FIG. 21, when the user walks
in the coverage area of the radio wave or the infrared ray
transmitted by the installed terminal 2 installed in the store A,
information indicating a moving path represented by a curved line
arrow along which the user walks from a store C to the store A via
a store B may be output to the installed terminal 2.
[0078] In a case where the installed terminal 2 is an image marker,
the broken circular line indicates an area in which an image of an
image marker recognized by the camera 124 installed on the position
measurement apparatus 1 has a size greater than a particular value,
and, within this area, the position measurement apparatus 1
receives absolute coordinates of the installed terminal 2.
[0079] In FIG. 22, it is assumed by way of example that the
installed terminal 2 transmits a Wi-Fi radio wave. In the example
illustrated in FIG. 22, the Wi-Fi radio wave transmitted by the
installed terminal 2 installed in each store is received by a
position measurement apparatus 1. When the user walks near the
store A, the Wi-Fi radio wave transmitted by the installed terminal
2 installed in the store A is received by the position measurement
apparatus 1 via the Wi-Fi receiver 123. Wi-Fi radio waves
transmitted by installed terminals 2 installed in the store B and
the store C are also received. By receiving a plurality of Wi-Fi
radio waves as described above, it becomes possible to obtain
absolute coordinates by calculating the coordinates of the current
position using coordinate information provided from each base
station and information indicating the radio wave strength.
[0080] As described above, when the position measurement apparatus
1 is operated in the position information acquisition system
together with installed terminals 2 having installation coordinate
information such as a beacon, a Wi-Fi, an image marker, or the
like, it is possible to effectively use the information about the
position of the user or information about the trajectory of the
moving path dependent on the movement of the user based on the
acquired absolute coordinates of the position measurement apparatus
1.
[0081] Note that, alternatively, the absolute coordinate
measurement unit 12 may measure absolute coordinates using another
known method.
Configuration of Correction Processing Unit 13
[0082] The correction processing unit 13 includes a storage unit
131 and a trajectory correction calculation unit 133. The
correction processing unit 13 also includes an absolute coordinate
acquisition unit 132 configured to acquire absolute coordinates
from the absolute coordinate measurement unit 12.
[0083] The correction processing unit 13 has a function of
correcting a position of the position measurement apparatus 1
estimated by the position estimation unit 11 based on absolute
coordinates of the position measurement apparatus 1 measured by the
absolute coordinate measurement unit 12. The correction processing
unit 13 determines an amount of distance correction to be made
every predetermined number of steps of the user and an amount of
angle correction to be made every predetermined number of steps of
the user based on information generated by the reliability
generation unit 115 in terms of a movement direction every
predetermined number of steps and reliability information
indicating a reliability value of a movement distance every
predetermined number of steps of the user, and movement information
generated by the movement information generation unit 118 in terms
of a movement direction every predetermined number of steps of the
user and a movement distance every predetermined number of steps of
the user. The correction processing unit 13 then corrects the
movement distance and the movement direction every predetermined
number of steps of the user starting from the latest
already-corrected position information according to the determined
distance correction amount every predetermined number of steps of
the user and the angle correction amount every predetermined number
of steps of the user.
[0084] The storage unit 131 is a storage configured to store
various kinds of data used by the correction processing unit 13.
The storage unit 131 may also store various programs for executing
functions of the position measurement apparatus 1. The storage unit
131 may be realized by one of or a combination of non-volatile
memories capable of rewriting contents stored therein such as an
EPROM, an EEPROM (registered trademark), an HDD, a flash memory,
etc.
[0085] The storage unit 131 includes a position information storage
unit 1311 configured to store corrected position information
corrected by the correction processing unit 13. The position
information storage unit 1311 stores a relative position of the
position measurement apparatus 1 calculated by the relative
coordinate calculation unit 116 in the position estimation unit 11.
The position information storage unit 1311 also stores position
information indicating a corrected position at an ith step of the
user represented in coordinates (xpi, ypi).
[0086] The storage unit 131 also includes an angle reliability
storage unit 1312 configured to store an angle reliability value
estimated by the angle reliability generation unit 1151 in the
position estimation unit 11 and a distance reliability storage unit
1313 configured to store a distance reliability value estimated by
the distance reliability generation unit 1152.
[0087] The storage unit 131 further includes a correction
completion flag storage unit 1314 configured to store information
indicating whether the position information at the ith step of the
user has been corrected or not.
[0088] The trajectory correction calculation unit 133 corrects the
movement trajectory of the position measurement apparatus 1 based
on the information stored in the storage unit 131 in terms of the
position information, the angle reliability value, the distance
reliability value, and the correction completion flag and the
absolute coordinates measured by the absolute coordinate
measurement unit 12.
Example of Position Measurement Using Gyro Sensor and Geomagnetic
Sensor
[0089] A specific example of the position measurement is described
below for a case where the gyro sensor 1113 and the geomagnetic
sensor 1112 are used.
[0090] The position measurement apparatus 1 corrects the trajectory
by correcting the movement direction (attitude) when the trajectory
of the movement of the device of interest being subjected to the
position measurement is output. The position measurement apparatus
1 measures the attitude and then measures the movement direction,
using the gyro sensor 1113 and the geomagnetic sensor 1112.
[0091] The movement direction calculation unit 113 in the movement
information generation unit 118 generates the information
associated with the movement direction by integrating the sensor
values acquired from the gyro sensor 1113.
[0092] In a case where there is a difference between an azimuth
angle (an angle about an axis defined in the zenith direction)
based on the sensor values of the gyro sensor 1113 and an azimuth
angle based on the sensor values of the geomagnetic sensor 1112,
this difference can cause the trajectory of the moving path
estimated by the position estimation unit 11 to deviate from the
correct trajectory of the moving path.
[0093] The reliability generation unit 115 generates the
reliability value of the angle by calculating the difference
between the information associated with the movement direction
obtained by integrating the values acquired from the gyro sensor
1113 and the information associated with the movement direction
acquired from the geomagnetic sensor 1112.
[0094] The trajectory correction calculation unit 133 performs a
trajectory correction, as described later, using the reliability
value of the angle determined based on the difference described
above. By using, in the trajectory correction, the reliability
value indicating the difference between the azimuth angle based on
the sensor values of the gyro sensor 1113 and the azimuth angle
based on the sensor values of the geomagnetic sensor 1112 as
described above, it becomes possible to make proper corrections at
a location where there is local distortion and at a location where
the trajectory has a correct shape.
[0095] In the present embodiment, the attitude information
associated with the position measurement apparatus 1 calculated
using the gyro sensor 1113 and the geomagnetic sensor 1112 is
subjected to a coordinate transformation (coordinate axis
transformation) process performed by the attitude information
generation unit 112 thereby generating relative position
information. The relative position information generated by the
attitude information generation unit 112 is stored, together with
the reliability value, in the storage unit 131 every step of the
user. Note that a known Kalman filter or the like may be used in
the coordinate transformation process performed by the attitude
information generation unit 112.
[0096] The correction of the moving path trajectory is performed in
response to measuring the absolute coordinates of the position
measurement apparatus 1 by the absolute coordinate measurement unit
12. The correction of the moving path trajectory is performed on
all pieces of uncorrected position information and all uncorrected
reliability values stored in the storage unit 131. The correction
of the moving path trajectory is performed over a whole correction
interval given by an interval of measuring absolute coordinates at
a time. The correction of the moving path trajectory is performed
on the position information of each step within the correction
interval using the reliability value corresponding to the position
information of each step. As a result, a local correction is
achieved.
Method of Trajectory Correction
[0097] When the information stored in the storage unit 131 includes
uncorrected position information and also includes an angle
reliability value and a distance reliability value corresponding to
the uncorrected position information, if the correction processing
unit 13 acquires absolute coordinates of the position measurement
apparatus 1 from the absolute coordinate measurement unit 12 via
the absolute coordinate acquisition unit 132, the correction
processing unit 13 performs a correction on the uncorrected
position information thereby correcting the trajectory of the
moving path of the position measurement apparatus 1.
[0098] FIG. 6 is a diagram illustrating variables used by the
trajectory correction calculation unit 133. FIG. 7 is a diagram
illustrating a trajectory of a movement of a position estimated by
the position estimation unit 11 and also illustrating a deviation
thereof from an actual movement trajectory. Let (x.sub.pi,
y.sub.pi) denote coordinates indicating a position of the user at
an ith step estimated by the position estimation unit 11 and stored
in the storage unit 131 of the correction processing unit 13 as
illustrated in FIG. 6 and FIG. 7. Furthermore, let (x.sub.qj,
y.sub.qj) denote jth absolute coordinates measured by the absolute
coordinate measurement unit 12 and stored in the storage unit 131
of the correction processing unit 13.
[0099] Let it be assumed here that among all pieces of position
information stored in the position information storage unit 1311,
the most lately corrected position information as of when jth
absolute coordinates are acquired is that with coordinates of an
n.sub.jth step, and a further trajectory correction is performed on
position information with coordinates of an n.sub.mth step to an
n.sub.m+1th step acquired within an absolute-coordinate-acquisition
interval from mth to (m+1)th absolute coordinates.
[0100] The position information associated with the ith step (where
i=n.sub.m) stored in the position information storage unit 1311 has
been already subjected to the trajectory correction when mth
absolute coordinates were acquired. Therefore, the further
trajectory correction is performed in a range i=n.sub.m+1 to
n.sub.m+1. Note that the correction completion flag is not set for
any data in the range from i=n.sub.m+1 to n.sub.m+1 stored in the
correction completion flag storage unit 1314, that is, the
correction has not been yet performed on the data in this
range.
[0101] Before the trajectory correction process is performed, the
trajectory correction calculation unit 133 determines the total sum
of angle reliability values and the total sum of distance
reliability values assigned to corresponding pieces of the
uncorrected position information associated with respective walking
steps estimated by the position estimation unit 11.
[0102] The trajectory correction calculation unit 133 then
determines the differences of the distance and the angle, measured
starting from the latest already-corrected position information,
from the distance and the angle determined from the absolute
coordinates measured by the absolute coordinate measurement unit
12. Furthermore, the trajectory correction calculation unit 133
determines the differences in the distance and the angle between
the latest estimated position information estimated by the position
estimation unit 11 and the latest already-corrected position
information.
[0103] The trajectory correction calculation unit 133 calculates
the movement distance L.sub.qm+1 from the mth absolute coordinates
to the (m+1)th absolute coordinates according to equation (1) shown
below.
L.sub.qm+1= {square root over
((x.sub.qm+1-x.sub.qm).sup.2+(y.sub.qm+1-y.sub.qm).sup.2)} (1)
[0104] Furthermore, the trajectory correction calculation unit 133
calculates the movement distance L.sub.pnm+1 estimated by the
position estimation unit 11 for a range corresponding to the
movement distance L.sub.qm+1 described above, according to equation
(2) shown below.
L p n m + 1 = ( x p n m + 1 - x p n m ) 2 + ( y p n m + 1 - y p n m
) 2 ( 2 ) ##EQU00001##
[0105] The trajectory correction calculation unit 133 calculates
the overall distance reliability value .beta. based on the total
sum of the distance reliability values according to equation (3)
shown below.
1 .beta. = x = n m + 1 n m + 1 1 .beta. x ( 3 ) ##EQU00002##
[0106] Using these equations (1) to (3), the trajectory correction
calculation unit 133 calculates and (m+1)th distance correction
coefficient .DELTA..beta..sub.m+1 according to equation the total
sum of the distance reliability values according (4) shown
below.
.DELTA. .beta. m + 1 = ( L q m + 1 / L p n m + 1 ) * .beta. ( 4 )
##EQU00003##
[0107] Furthermore, the trajectory correction calculation unit 133
calculates an inclination angle .theta..sub.qm+1 of a line
connecting mth and (m+1)th absolute coordinates according to
equation (5) shown below.
tan .theta. q m + 1 = x q m + 1 - x q m y q m + 1 - y q m ( 5 )
##EQU00004##
[0108] The trajectory correction calculation unit 133 calculates an
inclination angle .theta..sub.pnm+1 of a line connecting
coordinates at an n.sub.m+1th step and coordinates at an n.sub.mth
step in the position information according to equation (6) shown
below.
tan .theta. p n m + 1 = x p n m + 1 - x p n m y p n m + 1 - y p n m
( 6 ) ##EQU00005##
[0109] The trajectory correction calculation unit 133 calculates an
overall angle reliability value .alpha. based on the total sum of
angle reliability values according to equation (7) shown below.
1 .alpha. = x = n m + 1 n m + 1 1 .alpha. x ( 7 ) ##EQU00006##
[0110] The trajectory correction calculation unit 133 calculates an
(m+1)th angle correction coefficient .DELTA..alpha..sub.m+1
according to equation (8) shown below.
.DELTA. .alpha. m + 1 = ( .theta. q m + 1 - .theta. p n m + 1 ) *
.alpha. ( 8 ) ##EQU00007##
[0111] The trajectory correction calculation unit 133 performs the
correction process on the position information in the range of
i=n.sub.m+1 to n.sub.m+1 steps using the distance correction
coefficient .DELTA..beta..sub.m+1 calculated according to equation
(4) and the angle correction coefficient .DELTA..alpha..sub.m+1
calculated according to equation (8).
First-Stage Distance Correction
[0112] The trajectory correction calculation unit 133 repeatedly
adds the sum of the distance reliability value and .DELTA..beta. to
each movement distance. More specifically, the trajectory
correction calculation unit 133 performs a calculation according to
equations (9) and (10) shown below where x.sub.i denotes an x
component of coordinates of ith step position information, and
x'.sub.i denotes a corrected component.
x p n m ' = x p n m ( 9 ) x p i ' = ( x p i - x p i - 1 ) * 1
.beta. i * .DELTA. .beta. + x p i - 1 ' ( i = n m + 1 .about. n m +
1 ) ( 10 ) ##EQU00008##
[0113] The trajectory correction calculation unit 133 also performs
a calculation for a y component according to equations (11) and
(12) shown below where y.sub.i denotes the y component of
coordinates of ith step position information, and y'.sub.i denotes
a corrected component.
y p n m ' = y p n m ( 11 ) y p i ' = ( y p i - y p i - 1 ) * 1
.beta. i * .DELTA. .beta. + y p i - 1 ' ( i = n m + 1 .about. n m +
1 ) ( 12 ) ##EQU00009##
Angle Correction
[0114] The trajectory correction calculation unit 133 performs an
angle correction process on the coordinates (x'.sub.pi, y'.sub.pi),
which have been subjected to the first-stage distance correction,
using the angle reliability value and .DELTA..alpha.. Note that in
this angle correction process, the trajectory correction
calculation unit 133 uses an additional parameter V different from
.DELTA..alpha.. That is, the trajectory correction calculation unit
133 performs the angle correction process on the coordinates
(x'.sub.pi, y'.sub.pi), which have been subjected to the
first-stage distance correction, according to equations (13) to
(15) shown below.
.theta. p i ' = tan - 1 ( x p i ' - x p i - 1 ' y p i ' - y p i - 1
' ) ( 13 ) x p i '' = ( x p i ' - x p i - 1 ' ) * cos ( .theta. p i
+ 1 .alpha. i * .DELTA. .alpha. * V ) - ( y p i ' - y p i - 1 ' ) *
sin ( .theta. p i + 1 .alpha. i * .DELTA. .alpha. * V ) + x p i - 1
' ( i = n m + 1 .about. n m + 1 ) ( 14 ) y p i '' = ( y p i ' - y p
i - 1 ' ) * cos ( .theta. p i + 1 .alpha. i * .DELTA. .alpha. * V )
- ( x p i ' - x p i - 1 ' ) * sin ( .theta. p i + 1 .alpha. i *
.DELTA. .alpha. * V ) + y p i - 1 ' ( i = n m + 1 .about. n m + 1 )
( 15 ) ##EQU00010##
[0115] Furthermore, the trajectory correction calculation unit 133
calculates an inclination angle .theta.''.sub.pnm+1 between the
n.sub.mth walking step and the n.sub.m+1th walking step according
to equation (16) shown below.
.theta. p n m + 1 '' = tan - 1 ( x p n m + 1 '' - x p n m '' y p n
m + 1 '' - y p n m '' ) ( 16 ) ##EQU00011##
[0116] The trajectory correction calculation unit 133 compares the
calculated inclination angle .theta.''.sub.pnm+1 with the
inclination angle .theta..sub.qm+1 (equation (5)), and finds a
value of V that minimizes this difference and uses it. This value
of V may be determined, for example, using the Newton's method or
the like.
Second-Stage Distance Correction
[0117] In a case where the method of calculating the movement
distance is perfect, the first-stage distance correction and the
angle correction cause the position indicated by the n.sub.m+1th
step coordinates to be coincident with the position indicated by
the (m+1)th absolute coordinates. However, in practice, the
calculation method may not be perfect, and thus there may be
possibility that the position indicated by the n.sub.m+1th step
coordinates is not coincident with the position indicated by the
(m+1)th absolute coordinates. In such a case, the trajectory
correction calculation unit 133 enlarges or reduces the
angle-corrected moving path such that the n.sub.m+1th step position
is coincident with the position of the (m+1)th absolute
coordinates.
[0118] In a similar manner to the first-stage distance correction,
the trajectory correction calculation unit 133 calculates
L''.sub.pnm+1 and L.sub.qm+1 (according to equation (1)) and
calculates a processing factor .gamma. according to equations (17)
and (18) shown below.
L p n m + 1 '' = ( x p n m + 1 '' - x p n m '' ) 2 + ( y p n m + 1
'' - y p n m '' ) 2 ( 17 ) .gamma. = L q m + 1 L p n m + 1 '' ( 18
) ##EQU00012##
[0119] Using this .gamma., the trajectory correction calculation
unit 133 corrects the coordinates (x''.sub.pi, Y''.sub.pi)
(i=n.sub.m+1 to n.sub.m+1) according to equations (19) to (22)
thereby determining (x'''.sub.pi, y'''.sub.pi).
x p n m ''' = x p n m '' ( 19 ) x p i ''' = ( x p i '' - x p i - 1
'' ) * .gamma. + x p i - 1 '' ( i = n m + 1 .about. n m + 1 ) ( 20
) y p n m ''' = y p n m '' ( 21 ) y p i ''' = ( y p i '' - y p i -
1 '' ) * .gamma. + y p i - 1 '' ( i = n m + 1 .about. n m + 1 ) (
22 ) ##EQU00013##
[0120] The trajectory correction calculation unit 133 corrects
position information stored in the position information storage
unit 1311 associated with the (n.sub.m+1)th step to the n.sub.m+1th
step to (x'''.sub.pi, y'''.sub.pi) (i=n.sub.m+1 to n.sub.m+1).
Furthermore, the trajectory correction calculation unit 133 changes
the correction completion flag information stored in the correction
completion flag storage unit 1314 associated with the (n.sub.m+1)th
step to the n.sub.m+1th step such that the correction completion
flag information is set to indicate that the correction has been
made. Thus, the trajectory correction process performed by the
trajectory correction calculation unit 133 is completed.
Effects of the Present Embodiment
[0121] In a case where a movement trajectory is corrected by
performing rotating and/or enlarging according to a known related
technique, a destination point can be properly corrected, but a
correct trajectory may not be obtained for an intermediate moving
path as shown in FIG. 8. In contrast, when the correction method
according to the present embodiment is used, as shown in FIG. 9,
the moving path changes in response to changing the angle
correction coefficient V, and thus it is possible to minimize the
deviation of the movement trajectory from the correct moving path
by selecting an optimum value for the angle correction coefficient
V (in the example shown in FIG. 9, the deviation from the correct
moving path is minimized when V=0.5.DELTA..alpha.).
[0122] Furthermore, as shown in FIG. 10, if there is an abnormality
in geomagnetism, this may cause an error in the trajectory of
position estimated by the position estimation unit 11. In this
case, it is difficult to correct the trajectory by the rotation
and/or the enlargement according to the known related technique as
shown in FIG. 11. In contrast, when the correction method according
to the present embodiment is used, it is possible to obtain a
moving path very close to the correct moving path as shown in FIG.
12.
[0123] Note that constituent elements and configurations thereof of
the present embodiment are not limited to the examples described
above, but various replacements and modifications are possible. For
example, the installed terminal 2 such as a beacon, an image
marker, or the like may be installed in an area where position
information is to be acquired such that position information
associated with the user carrying the position measurement
apparatus 1 can be acquired in this area. In the present
embodiment, it is allowed to increase intervals at which the
position information represented by absolute coordinates is
acquired, and thus it is allowed to correspondingly increase the
intervals at which installed terminals 2 are installed, which
results in a reduction in the number of installed terminals 2.
[0124] In the present embodiment, as described above, use of the
reliability value of the position information determined every
walking step makes it possible to properly correct the trajectory
locally on a point-by-point bases. Therefore, even when the
frequency of receiving the GPS signal is reduced, it is possible to
maintain high accuracy of the trajectory.
Process Performed Position Estimation Unit 11
[0125] FIG. 13 is a flow chart illustrating a flow of a process
performed by the position estimation unit 11.
Step S21
[0126] The position estimation unit 11 acquires sensor values of
the respective sensors included in the sensor group 111.
Step S22
[0127] The position estimation unit 11 calculates the attitude of
the device of interest using a function of the attitude information
generation unit 112. The attitude information generation unit 112
provides, to the reliability generation unit 115, information
associated with the attitude obtained using a combination of the
sensor values of the acceleration sensor 1111 and the sensor values
of the geomagnetic sensor 1112 and also information associated with
the attitude obtained using the sensor values of the gyro sensor
1113.
Step S23
[0128] The position estimation unit 11 converts the coordinate axes
associated with the calculated attitude of the device of interest
by using a function of the attitude information generation unit 112
thereby generating attitude information. The attitude information
generation unit 112 provides the generated attitude information to
the movement information generation unit 118 and the reliability
generation unit 115.
Step S24
[0129] The movement information generation unit 118 performs the
principal component analysis on the horizontal acceleration
component of the attitude information generated by the attitude
information generation unit 112 by using a function of the movement
direction calculation unit 113, and the movement information
generation unit 118 employs a direction indicated by the first
principal component as the movement direction. The movement
information generation unit 118 provides a result of the principal
component analysis to the reliability generation unit 115.
Step S25
[0130] The movement information generation unit 118 generates,
using a function of the movement distance calculation unit 114,
information associated with the movement distance from the amount
of change of the sensor value in the vertical direction acquired
from the acceleration sensor 1111. The movement information
generation unit 118 may calculate, using a function of the movement
distance calculation unit 114, the length of stride from the
attitude information generated by the attitude information
generation unit 112 and the change in the acceleration in the
vertical direction, and may employ the calculated length of stride
as the information associated with the movement distance.
Step S26
[0131] The movement information generation unit 118 generates,
using a function of the movement distance calculation unit 114, the
movement distance in the vertical direction from the amount of
change of the sensor value acquired by the atmospheric pressure
sensor 1114. The movement information generation unit 118 provides
the generated information associated with the movement distance to
the reliability generation unit 115.
Step S27
[0132] The relative coordinate calculation unit 116 calculates the
relative position (relative coordinates) based on the length of
stride calculated by the movement distance calculation unit 114 and
the movement direction calculated by the movement direction
calculation unit 113, and the relative coordinate calculation unit
116 provides the calculated relative position (relative
coordinates) to the correction processing unit 13.
Step S28
[0133] The movement distance calculation unit 114 calculates the
movement distance based on the calculated length of stride and the
amount of change of the acceleration based on the sensor values
acquired by the acceleration sensor 1111. The movement distance
calculation unit 114 provides the calculated movement distance
based on the amount of change of the acceleration to the
reliability generation unit 115.
Step S29
[0134] The reliability generation unit 115 calculates .eta. based
on the difference between the movement distance calculated in step
S26 and the movement distance calculated in step S28. More
specifically, .eta. is calculated as
.eta.=L.sub.A/abs(L.sub.M-L.sub.A) where L.sub.M denotes the
distance obtained from the atmospheric pressure sensor and L.sub.A
denotes the distance obtained from the acceleration sensor.
Step S30
[0135] The reliability generation unit 115 determines the
difference .theta..sub.A in azimuth angle between the information,
calculated in step S22, associated with the attitude obtained from
the sensor value of the gyro sensor 1113 and the information
associated with the attitude obtained from the combination of the
sensor value of the acceleration sensor 1111 and the sensor value
of the geomagnetic sensor 1112. Furthermore, the reliability
generation unit 115 determines .theta..sub.B using the first
principal component and the second principal component obtained as
a result of the principal component analysis in step S24. The
reliability generation unit 115 generates reliability information
indicating the reliability value of the movement information using
.theta..sub.A, .theta..sub.B, and .eta. calculated in step S29. The
reliability generation unit 115 provides the generated reliability
information to the correction processing unit 13.
Step S31
[0136] The correction processing unit 13 stores, in the storage
unit 131, the relative position information calculated in step S27
and the reliability information generated in step S30.
[0137] Note that in step S30, the reliability generation unit 115
may generate only the reliability information indicating the
reliability value of the angle of the attitude based on the
difference .theta..sub.A of the azimuth angle between the
information associated with the attitude calculated in step S22
using the sensor values of the acceleration sensor 1111 and the
geomagnetic sensor 1112 and the information associated with the
attitude calculated using the sensor value of the gyro sensor 1113,
while the reliability value of the distance may be set to a fixed
value, for example, 1.
[0138] Alternatively, in step S30, the reliability generation unit
115 may determine .theta..sub.B based on the first principal
component and the second principal component obtained as a result
of the principal component analysis in step S24 and may generate
only the reliability information indicating the reliability value
of the angle of the movement direction based on .theta..sub.B,
while the reliability value of the angle of the attitude may be set
to a fixed value, for example, 1.
[0139] FIG. 14 is a diagram illustrating a manner of calculating
.theta..sub.B. The magnitude of the first principal component is
denoted by Lb, and The magnitude of the second principal component
is denoted by La. Ideally, La=0, and thus
.theta..sub.B=tan.sup.-1(La/Lb). By rotating the direction of the
first principal component by an amount corresponding to
.theta..sub.B, it is possible to achieve La=0.
[0140] FIG. 15A is a diagram illustrating an example of a result of
the principal component analysis. FIG. 15B is a diagram
illustrating an example of a result obtained when the first
principal component is rotated by an amount corresponding to
.theta..sub.B. As shown in FIGS. 15A and 15B, it is possible to
make La equal to 0 by making a correction by rotating the first
principal component by the amount corresponding to
.theta..sub.B.
[0141] In step S30, the reliability generation unit 115 may
generating only the reliability information indicating the
reliability value of the distance using .eta. calculated in step
S29, while the reliability value of the angle may be set to a fixed
value, for example, 1.
Process Performed by Correction Processing Unit 13
[0142] FIG. 16 is a flow chart illustrating a flow of a process
performed by the correction processing unit 13.
Step S41
[0143] The correction processing unit 13 receives information
associated with absolute coordinates indicating the position of the
position measurement apparatus 1 from the absolute coordinate
measurement unit 12. The correction processing unit 13 updates the
information associated with the absolute coordinates stored in the
storage unit 131.
Step S42
[0144] The correction processing unit 13 extracts N pieces of
uncorrected position information stored in the position information
storage unit 1311 based on the correction completion flags stored
in the correction completion flag storage unit 1314 in the storage
unit 131, and the correction processing unit 13 calculates the
total sum .alpha. of the reliability values of the angle and the
total sum .beta. of the reliability values of the distance. The
total sum .alpha. of the reliability values of the angle is
calculated according to equation (7) described above, and the total
sum .beta. of the reliability values of the distance is calculated
according to equation (3) described above.
Step S43
[0145] The correction processing unit 13 calculates, using a
function of the trajectory correction calculation unit 133, the
distance L1 and the angle .theta.1 as seen from the latest
already-corrected position information to the latest relative
coordinates calculated by the relative coordinate calculation unit
116. The distance L1 is calculated according to equation (2)
described above, and the angle .theta.1 is calculated according to
equation (6) described above. The correction processing unit 13
calculates, using a function of the trajectory correction
calculation unit 133, the distance L2 and the angle .theta.2 from
the latest already-corrected position information to the absolute
coordinates indicating the position of the position measurement
apparatus 1 received in step S41. The distance L2 is calculated
according to equation (1) described above, and the angle .theta.2
is calculated according to equation (5) described above.
[0146] The process from step S41 to step S43 is performed by the
trajectory correction calculation unit 133 as a preliminary process
for the correction.
Step S44
[0147] The correction processing unit 13 calculates the distance
correction coefficient .DELTA..beta. using a function of the
trajectory correction calculation unit 133. .DELTA..beta. may be
calculated such that .DELTA..beta.=(L2-L1).times..beta.. In the
process in step S44, equation (4) described above is used.
Step S45
[0148] Using a function of the trajectory correction calculation
unit 133, the correction processing unit 13 multiples the distance
of every walking step by the reliability value of the distance for
the N pieces of the uncorrected position information. In step S45,
equations (9) to (12) described above are used.
[0149] The above-described process in steps S44 and S45 is
performed by the trajectory correction calculation unit 133 as a
first-stage process of the distance correction, and the correction
amount is obtained by multiplying .DELTA..beta. calculated in step
S44 by the reliability value of the distance. Thus, the corrected
coordinates are given as (x'.sub.pi, y'.sub.pi).
[0150] The distance moved every walking step is equal to the length
of stride, and the length of stride from an ith step to an (i+1)th
step can be determined according to equation (23) shown below.
Length of stride=
((X.sub.i+1-X.sub.i).sup.2+(Y.sub.i+1-Y.sub.i).sup.2) (23)
Step S46
[0151] The correction processing unit 13 calculates the angle
correction coefficient .DELTA..alpha. using a function of the
trajectory correction calculation unit 133. More specifically,
using the angle .theta.1 and the angle .theta.2 obtained in step
S43, .DELTA..alpha. can be calculated as
.DELTA..alpha.=(.theta.2-.theta.1).times..alpha.. In the process
step S46, equation (8) described above is used.
Step S47
[0152] the trajectory correction calculation unit 133 determines
whether .theta.1-.theta.2.apprxeq.0. In a case where the trajectory
correction calculation unit 133 determines that
.theta.1-.theta.2.apprxeq.0 (Yes in step S47), the trajectory
correction calculation unit 133 performs the process according to
equations (14) to (16) described above thereby obtaining corrected
coordinates (x''.sub.pi, y''.sub.pi). Thereafter, the processing
flow proceeds to step S50. However, in a case where the
determination by the trajectory correction calculation unit 133
denies that .theta.1-.theta.2.apprxeq.0 (No in step S47), the
processing flow proceeds to step S48.
Step S48
[0153] The trajectory correction calculation unit 133 corrects the
movement direction every walking step for each of the N pieces of
uncorrected position information such that
.DELTA..alpha..times.angle reliability value is employed as the
angle correction amount, and the movement direction in every
walking step is rotated by the angle correction amount.
[0154] The movement direction in the ith step to the (i+1)th step
can be determined according to equation (24) shown below.
Movement
direction=tan.sup.-1((X.sub.i+1-X.sub.i)/(Y.sub.i+1-Y.sub.i)
(24)
Step S49
[0155] The trajectory correction calculation unit 133 performs a
recalculation of the angle .theta.1 on the latest already-corrected
relative coordinates and updates the value of A according to the
value of .theta.1-.theta.2. Thereafter, the processing flow returns
to step S47. In the recalculation of the angle .theta.1, equation
(13) described above is used. More specifically, the trajectory
correction calculation unit 133 updates the value of .DELTA..alpha.
according to the value of .theta.1-.theta.2 using a known method
such as the Newton's method or the like.
[0156] The above-described process in steps S46 to S49 is performed
by the trajectory correction calculation unit 133 as the angle
correction process and the angle correction amount is determined
such that .theta.1-.theta.2.apprxeq.0.
Step S50
[0157] The trajectory correction calculation unit 133 performs a
recalculation of the distance L1 on the latest already-corrected
relative coordinates. In the calculation of the distance L1,
equation (17) described above is used.
Step S51
[0158] The trajectory correction calculation unit 133 calculates
the distance correction factor .gamma. for the recalculated
distance L1. .gamma. can be calculated as .gamma.=L2/L1. That is,
the process in step S51 is performed according to equation (18)
described above.
Step S52
[0159] The trajectory correction calculation unit 133 multiplies
the distance in each walking step by y for the N pieces of
uncorrected position information according to equations (19) to
(22). Thus, the correction process is completed and the corrected
coordinates are given as (x'''.sub.pi, y'''.sub.pi).
[0160] The above-described process in steps S50 to S52 by the
trajectory correction calculation unit 133 is performed as a
second-stage process of the distance correction.
[0161] In the example described above, the correction in terms of
the movement distance and the movement direction by the correction
processing unit 13 is performed on the N pieces of uncorrected
position information for every walking step. However, in stead of
performing the correction every walking step, the correction may be
performed every predetermined number of walking steps.
Second Embodiment
[0162] A second embodiment of the present disclosure is described
below. For convenience of illustration, elements or units having
similar functions to those described in the first embodiment are
denoted by similar reference numerals, and a description thereof is
omitted.
[0163] In the position measurement apparatus 1 according to the
second embodiment, an amount of change of a magnitude of a
resultant vector of vectors along three axes of the geomagnetic
sensor 1112 is added as one of factors based on which the angle
reliability value is calculated by the angle reliability generation
unit 1151 shown in FIG. 1.
[0164] The movement direction calculation unit 113 in the movement
information generation unit 118 generates information associated
with the movement direction of the position measurement apparatus 1
from the resultant vector of vectors along three axes based on the
sensor values of the geomagnetic sensor 1112. When a magnetic field
exists near the geomagnetic sensor 1112, the geomagnetic sensor
1112 detects this magnetic field, and the magnitude of the
resultant vector of vectors along three axes may be disturbed by
the magnetic field. The angle reliability generation unit 1151
generates the reliability value of the angle by calculating the
amount of change of the information associated with the movement
direction obtained from the magnitude of the resultant vector of
vectors along three axes based on the sensor values of the
geomagnetic sensor 1112. More specifically, the angle reliability
generation unit 1151 determines that the smaller the amount of
change of the magnitude of the resultant vector of vectors along
three axes based on the sensor values of the geomagnetic sensor
1112, the smaller the error is. The angle reliability generation
unit 1151 employs, as the reliability value, the value whose
numerator is 1 and whose denominator is given by the sum of amounts
of change of the resultant vector of vectors along three axes of
the geomagnetic sensor 1112 each of which is detected every walking
step. Note that the position measurement apparatus 1 according to
the second embodiment performs the same process as that performed
according to the first embodiment except that the amount of change
of the magnitude of the resultant vector of vectors along three
axes of the geomagnetic sensor 1112 is added as one of factors
based on which the angle reliability value is calculated by the
angle reliability generation unit 1151.
Third Embodiment
[0165] A third embodiment of the present disclosure is described
below. For convenience of illustration, elements or units having
similar functions to those described in the first embodiment are
denoted by similar reference numerals, and a description thereof is
omitted.
[0166] In the position measurement apparatus 1 according to the
third embodiment, the amount of change of the magnetic inclination
indicated by the geomagnetic sensor 1112 is added as one of factors
based on which the angle reliability value is calculated by the
angle reliability generation unit 1151 shown in FIG. 1. The
movement direction calculation unit 113 in the movement information
generation unit 118 generates information associated with the
movement direction from the magnetic inclination of the position
measurement apparatus 1 based on the sensor values of the
geomagnetic sensor 1112.
[0167] When a nonmagnetic material exists near the geomagnetic
sensor 1112, distortion occurs in the direction of the magnetism,
and thus the direction indicated by the geomagnetic sensor 1112 may
be different from the magnetic north direction. This result in a
possibility that an error occurs in the magnetic inclination, which
changes depending on latitude and longitude but does not
significantly change during a movement of about several hundred
meters in an ordinal circumstance. In view of the above, the angle
reliability generation unit 1151 generates the reliability value of
the angle by calculating the amount of change of the information
associated with the movement direction obtained from the magnetic
inclination of the position measurement apparatus 1 based on the
sensor values of the geomagnetic sensor 1112.
[0168] More specifically, the angle reliability generation unit
1151 determines that the smaller the amount of change of the
magnetic inclination indicated by the geomagnetic sensor 1112, the
smaller the error is. The angle reliability generation unit 1151
employs, as the reliability value, the value whose numerator is 1
and whose denominator is given by the sum of amount of changes of
the magnetic inclinations of the geomagnetic sensor 1112 detected
on a step-by-step basis during walking. Note that the position
measurement apparatus 1 according to the third embodiment performs
the same process as that performed according to the first
embodiment except that the amount of change of the magnetic
inclination indicated by the geomagnetic sensor 1112 is added as
one of factors based on which the angle reliability value is
calculated by the angle reliability generation unit 1151.
Fourth Embodiment
[0169] A fourth embodiment of the present disclosure is described
below. For convenience of illustration, elements or units having
similar functions to those described in the first embodiment are
denoted by similar reference numerals, and a description thereof is
omitted.
[0170] In the position measurement apparatus 1 according to the
fourth embodiment, the amounts of changes of the derivatives of the
sensor values of the gyro sensor 1113 are added as one of factors
based on which the angle reliability value is calculated by the
angle reliability generation unit 1151 shown in FIG. 1. The
movement information generation unit 118 generates the information
associated with the movement direction from the derivatives of the
sensor values of the gyro sensor 1113.
[0171] When a human being walks, he/she moves alternately right and
left legs, which causes a turning motion from side to side to occur
during walking. As shown in FIGS. 20A to 20C, if an impact such as
an unusual sudden motion of a body occurs as in an area 1) or an
area 2) shown in FIG. 20A in the middle of an ideal regular motion
of a waist, a change occurs in an amount of change of a sensor
value of the gyro sensor 1113 or the gyro sensor 1113 as shown in
FIG. 20B or 20C.
[0172] Such a change in a sensor value of the gyro sensor 1113 or a
change in an amount of change of a sensor value of the gyro sensor
1113 can cause a reduction in the accuracy of the position
measurement. A change caused by a sudden impact can result in a
greater change in an amount of change of a sensor value of the gyro
sensor 1113 than in the sensor value of the gyro sensor 1113.
Therefore, in the present embodiment, an amount of change of a gyro
sensor value is used as a factor based on which the angle
reliability value is calculated by the angle reliability generation
unit 1151.
[0173] The angle reliability generation unit 1151 determines the
derivatives of the sensor values in the respective directions along
the three axes of the gyro sensor 1113, and generates the
reliability value of the angle by calculating the amount of change
of the information associated with the movement direction obtained
from the derivatives. More specifically, the angle reliability
generation unit 1151 determines that the smaller the amount of
changes of the sensor values of the gyro sensor 1113, the smaller
the error is. The angle reliability generation unit 1151 employs,
as the reliability value, the value whose numerator is 1 and whose
denominator is given by the sum of absolute values of amount of
changes of the sensor values of the gyro sensor 1113 detected on a
step-by-step basis during walking. Note that the position
measurement apparatus 1 according to the fourth embodiment performs
the same process as that performed according to the first
embodiment except that the amount of change of the sensor value of
the gyro sensor 1113 is added as one of factors based on which the
angle reliability value is calculated by the angle reliability
generation unit 1151.
Fifth Embodiment
[0174] A fifth embodiment of the present disclosure is described
below. For convenience of illustration, elements or units having
similar functions to those described in the first embodiment are
denoted by similar reference numerals, and a description thereof is
omitted.
[0175] In the position measurement apparatus 1 according to the
fifth embodiment, the difference between the angle of the attitude
calculated from the sensor value of the acceleration sensor 1111
and that calculated from the sensor value of the geomagnetic sensor
1112 is added as one of factors based on which the angle
reliability value is calculated by the angle reliability generation
unit 1151. When only the gravitational acceleration component is
considered, the rotation angle about the coordinate axis
perpendicular to the vertical direction can be determined from the
sensor value of the acceleration sensor 1111. The rotation angle
about the coordinate axis perpendicular to the vertical direction
corresponds to a pitch angle or a roll angle in the airplane
control or the like. The pitch angle or the roll angle can also be
determined from the sensor values of the geomagnetic sensor
1112.
[0176] The attitude information generation unit 112 determines the
rotation angle about the coordinate axis perpendicular to the
vertical direction based on the sensor value of the acceleration
sensor 1111 and also the rotation angle based on the sensor value
of the geomagnetic sensor 1112, and generates the attitude
information using the determined rotation angles.
[0177] The angle reliability generation unit 1151 generates the
reliability value of the angle based on the difference between the
angle associated with the attitude information based on the sensor
value of the acceleration sensor 1111 and the angle associated with
the attitude information based on the sensor value of the
geomagnetic sensor 1112. More specifically, the angle reliability
generation unit 1151 determines that the smaller the difference
between the angle of the attitude based on the sensor value of the
acceleration sensor 1111 and the angle of the attitude based on the
sensor value of the geomagnetic sensor 1112, the smaller the error
is. The angle reliability generation unit 1151 employs, as the
reliability value, the value whose numerator is 1 and whose
denominator is given by the sum of absolute values of differences
between the absolute value of the difference of the pitch angle and
the absolute value of the roll angle detected for every walking
step. Note that the position measurement apparatus 1 according to
the fifth embodiment performs the same process as that performed
according to the first embodiment except that the difference
between the angle of the attitude calculated from the sensor value
of the acceleration sensor 1111 and the angle of the attitude
calculated from the sensor value of the geomagnetic sensor 1112 is
added as one of factors based on which the angle reliability value
is calculated by the angle reliability generation unit 1151.
Sixth Embodiment
[0178] A sixth embodiment of the present disclosure is described
below. For convenience of illustration, elements or units having
similar functions to those described in the first embodiment are
denoted by similar reference numerals, and a description thereof is
omitted.
[0179] In the position measurement apparatus 1 according to the
sixth embodiment, the difference of the amount of change of the
velocity obtained by dividing the movement distance determined from
the sensor value of the acceleration sensor 1111 by the time taken
by the user to walk every predetermined number of steps (for
example, one step) is added as one of factors based on which the
distance reliability value is calculated by the distance
reliability generation unit 1152 shown in FIG. 1.
[0180] The movement distance calculation unit 114 of the movement
information generation unit 118 generates the information
associated with the movement distance from the amount of change of
the velocity obtained by dividing the sensor value of the
acceleration sensor 1111 by the moving time taken by the user to
walk every predetermined number of steps.
[0181] In a circumstance in which no change occurs in conditions of
the ground such as a slant and/or the like, human beings walk at a
substantially constant walking speed. Therefore, the distance
reliability generation unit 1152 determines that the smaller the
difference of the walking speed detected every step from the
average speed is, the smaller the error is. The distance
reliability generation unit 1152 generates the reliability value of
the distance based on the difference, from the average moving time
of the user, of the information associated with the movement
distance obtained from the amount of change of the velocity
determined by dividing the sensor value of the acceleration sensor
1111 by the moving time taken by the user to walk every
predetermined number of steps. For example, the distance
reliability generation unit 1152 employs, as the reliability value,
the value whose numerator is 1 and whose denominator is given by
the difference of the velocity of the user in walking every
predetermined number of steps from the average velocity of the
moving time of the user. Note that the position measurement
apparatus 1 according to the sixth embodiment performs the same
process as that performed according to the first embodiment except
that the difference of the amount of change of the velocity
determined by dividing the movement distance calculated from the
sensor value of the acceleration sensor 1111 by the time taken to
walk one step is added as one of factors based on which the
distance reliability value is calculated by the distance
reliability generation unit 1152.
Modifications
[0182] The position measurement apparatus 1 may be realized by
combining constituent elements used in the first to sixth
embodiments described above. More specifically, as one of factors
based on which the angle reliability value is calculated by the
angle reliability generation unit 1151 of the position measurement
apparatus 1 according to the first embodiment, at least one of the
following values may be added: the amount of change of the
magnitude of the resultant vector of vectors along three axes of
the geomagnetic sensor 1112; the amount of change of the magnetic
inclination indicated by the geomagnetic sensor 1112; the amount of
change of the derivative of the sensor value of the gyro sensor
1113; and the difference between the angle of the attitude
calculated from the sensor value of the acceleration sensor 1111
and the angle of the attitude calculated from the sensor value of
the geomagnetic sensor 1112. As one of factors based on which the
distance reliability value is calculated by the distance
reliability generation unit 1152 of the position measurement
apparatus 1 according to the first embodiment, the following value
may be added, that is, the difference of the amount of change of
the velocity obtained by dividing the movement distance determined
from the sensor value of the acceleration sensor 1111 by the time
taken by the user to walk every predetermined number of steps (for
example, every one step). That is, the sensor group 111 of the
position measurement apparatus 1 includes at least one of the
following sensors: the gyro sensor 1113; the geomagnetic sensor
1112; the acceleration sensor 1111, and the atmospheric pressure
sensor 1114.
[0183] The reliability generation unit 115 performs a combination
including a plurality of the following processes: the process of
generating the reliability value of the angle from the ratio of the
first principal component to the second principal component of the
information associated with the movement direction; the process of
generating a reliability value of the angle by calculating the
difference between information associated with the movement
direction obtained by integrating the value acquired from the gyro
sensor 1113 and the information associated with the movement
direction acquired from the geomagnetic sensor 1112; the process of
generating the reliability value of the angle by calculating the
amount of change of the information associated with the movement
direction obtained from the magnitude of the resultant vector of
vectors along three axes of the geomagnetic sensor 1112; the
process of generating the reliability value of the angle by
calculating the amount of change of the information associated with
the movement direction obtained from the magnetic inclination of
the geomagnetic sensor 1112; the process of generating the
reliability value of the angle by calculating the amount of change
of the information associated with the movement direction obtained
from the derivatives along the three axes of the gyro sensor 1113;
the process of generating the reliability value of the angle from
the difference between the angle associated with the attitude
information based on the sensor value of the acceleration sensor
1111 and the angle associated with the attitude information based
on the sensor value of the geomagnetic sensor 1112; the process of
generating the reliability value of the distance from the
difference between the movement distance obtained from the amount
of change of the atmospheric pressure sensor 1114 and the movement
distance obtained from the amount of change of the acceleration
sensor 1111; and the process of generating the reliability value of
the distance from the difference, from the average velocity of the
moving time of the user, of the information associated with the
movement distance obtained from the amount of change of the
velocity determined by dividing the value of the acceleration
sensor 1111 by the moving time taken by the user to walk every
predetermined number of steps.
Examples of Implementations Using Software
[0184] The control blocks of the position measurement apparatus 1
(in particular, the attitude information generation unit 112, the
reliability generation unit 115, and the trajectory correction
calculation unit 133) may be realized using a logic circuit
(hardware) formed on an integrated circuit (an IC chip) or may be
realized by software.
[0185] In the latter case, the position measurement apparatus 1
includes a computer configured to execute an instruction of a
program which is software for realizing each function. The computer
includes at least one processor (a control apparatus) and also at
least one computer-readable storage medium in which the program is
stored. In the computer, the processor reads out the program from
the storage medium and executes it thereby achieving the function
according to the present disclosure. A for the process, for
example, a CPU (Central Processing Unit) may be used. As for the
storage medium, a non-transitory tangible medium such as a ROM
(Read Only Memory), a tape, a disk, a card, a semiconductor memory,
a programmable logic circuit, or the like may be used. The computer
may further include a RAM (Random Access Memory) or the like in
which the program is loaded. The program may be supplied to the
computer via any transmission medium (a communication network, a
broadcast wave, or the like) capable of transmitting the program.
In an aspect, the present disclosure may be implemented in the form
of a data signal embedded in a carrier wave such that the program
is embodied by electric transmission of the program.
Summary of Embodiments
[0186] In Aspect 1 of the present disclosure, a position
measurement apparatus (1) includes a position estimation unit (11)
configured to estimate a position of a device of interest based on
a sensor value acquired from a sensor, an absolute coordinate
measurement unit (12) configured to measure absolute coordinates of
the device of interest; and, a correction processing unit (13)
configured to correct the position of the device of interest
estimated by the position estimation unit (11) based on the
absolute coordinates of the device of interest measured by the
absolute coordinate measurement unit (12), the position estimation
unit (11) including an attitude information generation unit (112)
configured to generate attitude information associated with the
device of interest based on the sensor value, a movement
information generation unit (118) configured to generate, based on
the attitude information, movement information including a movement
distance of the device of interest and a movement direction of the
device of interest, and a reliability generation unit (115)
configured to generate, based on the sensor value, reliability
information indicating a reliability value of the movement
information, the correction processing unit (13) being configured
to determine an amount of distance correction to be made every
predetermined number of steps and an amount of angle correction to
be made every predetermined number of steps based on the
reliability information and the movement information, and correct
the movement distance and the angle every predetermine number of
steps starting from latest already-corrected position information
associated with the device of interest.
[0187] The configuration described above makes it possible to
achieve high accuracy in the trajectory by correcting the distance
and the angle every predetermined number of walking steps even in a
state in which the frequency of acquiring absolute coordinates is
reduced.
[0188] In the position measurement apparatus (1) according to
Aspect 2 of the present disclosure, based on Aspect 1, the movement
information generation unit (118) may generate information
associated with the movement direction by performing a principal
component analysis on a horizontal acceleration included in the
attitude information, and the reliability generation unit (115) may
generate a reliability value of an angle from a ratio of a first
principal component to a second principal component included in the
information associated with the movement direction.
[0189] In the position measurement apparatus (1) according to
Aspect 3 of the present disclosure, based on Aspect 1, the sensor
may include a gyro sensor (1113) and a geomagnetic sensor (1112),
the movement information generation unit (118) may generate the
information associated with the movement direction by integrating a
value acquired from the gyro sensor (1113), and the reliability
generation unit (115) may generate a reliability value of an angle
by calculating a difference between the information associated with
the movement direction obtained by integrating the value obtained
from the gyro sensor (1113) and information associated with the
movement direction acquired from the geomagnetic sensor (1112).
[0190] In the position measurement apparatus (1) according to
Aspect 4 of the present disclosure, based on Aspect 1, the sensor
may include a geomagnetism sensor (1112), the movement information
generation unit (118) may generate the information associated with
the movement direction from a resultant vector of vectors along
three axes obtained from the geomagnetic sensor (1112), and the
reliability generation unit (115) may generate a reliability value
of an angle by calculating an amount of change of the information
associated with the movement direction obtained from a magnitude of
the resultant vector of vectors along three axes obtained from the
geomagnetic sensor (1112).
[0191] In the position measurement apparatus (1) according to
Aspect 5 of the present disclosure, based on Aspect 1, the sensor
may include a geomagnetism sensor (1112), the movement information
generation unit (118) may generate the information associated with
the movement direction from a magnetic inclination of the
geomagnetic sensor (1112), and the reliability generation unit
(115) may generate a reliability value of an angle by calculating
an amount of change of the information associated with the movement
direction obtained from the magnetic inclination of the geomagnetic
sensor (1112).
[0192] In the position measurement apparatus (1) according to
Aspect 6 of the present disclosure, based on Aspect 1, the sensor
may include a gyro sensor (1113), the movement information
generation unit (118) may generate the information associated with
the movement direction by differentiating a value acquired from the
gyro sensor (1113), and the reliability generation unit (115) may
generate a reliability value of an angle by calculating an amount
of change of the information associated with the movement direction
obtained from derivatives along the three axes of the gyro sensor
(1113).
[0193] In the position measurement apparatus (1) according to
Aspect 7 of the present disclosure, based on Aspect 1, the sensor
may include an acceleration sensor (1111) and a geomagnetic sensor
(1112), the attitude information generation unit (112) may generate
attitude information corresponding to a sensor value of the
acceleration sensor (1111) and a sensor value of the geomagnetic
sensor (1112), and the reliability generation unit (115) may
generate a reliability value of an angle from a difference in angle
between the attitude information corresponding to the sensor value
of the acceleration sensor (1111) and the attitude information
corresponding to the sensor value of the geomagnetic sensor
(1112).
[0194] In the position measurement apparatus (1) according to
Aspect 8 of the present disclosure, based on Aspect 1, the sensor
may include an acceleration sensor (1111), a geomagnetic sensor
(1112), and a gyro sensor (1113), the attitude information
generation unit (112) may generate attitude information by using a
combination of the acceleration sensor (1111) and the geomagnetic
sensor (1112), and the gyro sensor (1113), and the reliability
generation unit (115) may generate a reliability value of an angle
from a difference in azimuth angle between the attitude information
obtained by the gyro sensor (1113) and the attitude information
obtained by the combination of the acceleration sensor (1111) and
the geomagnetic sensor (1112).
[0195] In the position measurement apparatus (1) according to
Aspect 9 of the present disclosure, based on Aspect 1, the sensor
may include an acceleration sensor (1111) and an atmospheric
pressure sensor (1114), the movement information generation unit
(118) may generate information associated with the movement
distance from an amount of change of a sensor value of the
atmospheric pressure sensor (1114) and may generate information
associated with the movement distance from an amount of change in
the vertical direction of a sensor value of the acceleration sensor
(1111), and the reliability generation unit may generate a
reliability value of the distance from a difference between the
distance obtained by the atmospheric pressure sensor (1114) and the
distance obtained by the acceleration sensor (1111).
[0196] In the position measurement apparatus (1) according to
Aspect 10 of the present disclosure, based on Aspect 1, the sensor
may include an acceleration sensor (1111), the movement information
generation unit (118) may generate the information associated with
the movement distance from an amount of change of a velocity
obtained by dividing a value of the acceleration sensor (1111) by a
moving time taken for the user to move a predetermined number of
steps, and the reliability generation unit (115) may generate the
reliability value of the distance from a difference, from an
average moving time of the user, of information associated with the
movement distance obtained from an amount of change of a velocity
obtained by dividing a value of the acceleration sensor (1111) by a
moving time taken for the user to move a predetermined number of
walking steps.
[0197] In the position measurement apparatus (1) according to
Aspect 12 of the present disclosure, based on one of Aspects 1 to
11, the absolute coordinate measurement unit (12) may measure the
absolute coordinates by acquiring a GPS signal.
[0198] In the position measurement apparatus (1) according to
Aspect 13 of the present disclosure, based on one of Aspects 1 to
11, the absolute coordinate measurement unit (12) may measure the
absolute coordinates by receiving a beacon radio wave.
[0199] In the position measurement apparatus (1) according to
Aspect 14 of the present disclosure, based on one of Aspects 1 to
11, the absolute coordinate measurement unit (12) may measure the
absolute coordinates by receiving a Wi-Fi radio wave.
[0200] In the position measurement apparatus (1) according to
Aspect 15 of the present disclosure, based on one of Aspects 1 to
11, the absolute coordinate measurement unit (12) may measure the
absolute coordinates by acquiring an image marker.
[0201] The position measurement apparatus 1 according to any one of
Aspects of the present disclosure may be realized by a computer. In
this case, a control program controls the computer so as to operate
as units (software elements) included in the position measurement
apparatus 1 thereby realizing the position measurement apparatus 1
on the computer. The control program configured to control the
computer so as to realize the position measurement apparatus 1, and
a computer-readable storage medium in which the control program is
stored fall into the scope of the present disclosure.
[0202] The present disclosure is not limited to the embodiments
described above, but various modifications are possible within the
scope described in claims. Embodiments may also be possible by
properly combining technical means disclosed in different
embodiments, and the resultant embodiments fall within the
technical scope of the present disclosure. Furthermore, by
combining technical means disclosed in embodiments, it is possible
to create a new technical feature.
[0203] The present disclosure contains subject matter related to
that disclosed in Japanese Priority Patent Application JP
2018-033658 filed in the Japan Patent Office on Feb. 27, 2018, the
entire contents of which are hereby incorporated by reference.
[0204] It should be understood by those skilled in the art that
various modifications, combinations, sub-combinations and
alterations may occur depending on design requirements and other
factors insofar as they are within the scope of the appended claims
or the equivalents thereof.
* * * * *
References